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Carlo Rovelli’s review “White Holes: Inside the Horizon” challenges conventional notions of time.


I read A Brief History of Time by Stephen Hawking over 30 years ago. It opened my eyes to the marvels of the universe in a way that nothing else had before. While I may not have fully grasped it then, and perhaps still don’t, it definitely felt like an exciting journey. Carlo Rovelli’s latest book serves as a non-linear continuation, where he presents his concept of “white holes” and discusses their potential formation and the challenges in observing them in our universe presently.

Massive stars, upon reaching the end of their lifespan and depleting all of their fuel, collapse to create black holes. These peculiar objects have such strong gravitational pull that even light cannot escape from them. The existence of black holes was foreseen by Albert Einstein’s theory of general relativity, which posited them as entities where space and time cease to exist.

However, the very same mathematical equations used in physics to predict the presence of black holes also predict the existence of their opposite: white holes. These are objects that cannot be entered and only emit matter. While astronomers can observe black holes, or at least detect their effects as they consume matter in faraway galaxies, there is a lack of evidence for white holes. This has raised some speculation about their possible non-existence.

Carlo Rovelli

However, Rovelli holds strong convictions. His latest publication details his concept of white holes forming. He takes readers on a journey, beginning by entering a black hole and crossing its event horizon into its throat. Despite the expectation of reaching a dead end, Rovelli deviates from the traditional narrative and presents a novel perspective. This is a black hole, where everything is supposed to come to an end – space and time included. Yet in Rovelli’s understanding of the universe, this is not the case.

Rovelli is a highly skilled physicist, prolific writer, and eloquent science communicator. White Holes, his latest book, is compact but covers a vast amount of information at a rapid pace. It essentially condenses the entire content of A Brief History of Time into a few brief chapters, serving as an overview and introduction. Reading it is reminiscent of the trippy finale in the film 2001: A Space Odyssey – you’re not entirely sure where you’re going, but it’s exhilarating.

Rovelli takes the reader deep into a black hole in a shorter amount of pages than other writers would use to explain making an omelette. He proposes that as the star collapses, it becomes incredibly small and dense, causing the principles of general relativity to be replaced by those of quantum mechanics.

Quantum theory is the physics of uncertainty on a tiny scale. Here, particles and patches of space become clouds of probability and the previously impossible becomes possible. All of which Rovelli exploits to suggest that the star at the centre of a black hole, trying to collapse away to nothing, might reach a point at which quantum uncertainty allows it to “bounce” backward through time and become a white hole.

It is challenging to produce high-quality literature on extreme cosmic objects, as they are best understood through mathematical language. In fact, a complete understanding of these theories can only be achieved through the use of mathematics. Therefore, even the most detailed and extensive popular science book will fall short without the inclusion of complex symbols and equations.

However, this is a book written for the general reader and Rovelli is aware of this constraint. He briefly covers intricate details in order to convey the awe-inspiring essence of the universe and his theories. This approach proves to be effective in his hands.

Rovelli’s idea flips your understanding upside down. Instead of a black hole, which only sucks things in with no escape, he introduces the concept of a white hole, which only spews things out. He reverses the direction of time and sheds light on how white holes could potentially develop, while also explaining why astronomers have not observed them ejecting matter into the universe like Regan in The Exorcist.

Although the book is short, Rovelli is not afraid to address complex ideas. He cautions readers that some concepts may be challenging to understand. Personally, I am still unsure if my inability to recall the future is simply a trick of perception or a fundamental principle of physics. However, Rovelli assures readers that these details are not crucial, and what truly matters is the feeling of being transported through the book. If this is the case, then the book fulfills its purpose and more.

One of the things I most loved about White Holes was the glimpse Rovelli gives you into the mind of a physicist working at the edges of the known universe, and the fundamental insecurity of creating groundbreaking theories and then putting them out there like clay pigeons launched from a trap. It’s a strange duality. On the one hand, you have to be rock solid sure of the ideas you propose. But on the way to assembling them – and afterwards – you have to have the discipline to doubt them and continue to test them as fiercely as your staunchest rivals might.

Rovelli expresses concern about the book and its structure, noting that his strongest critics are students of physics who may take issue with the lack of in-depth explanations. This volume may not meet the needs of a final year undergraduate seeking revision materials for a high energy astrophysics module. However, for those seeking to rekindle their passion for the concept of the universe or discover it for the first time, this book is a perfect choice. Personally, I thoroughly enjoyed delving into Rovelli’s fascinating and unconventional universe.


Dr. Kevin Fong is a medical professional, media personality, and writer.

Source: theguardian.com